How soon you can change employer? (Singapore)

Hi everybody. I have this question and I want to know if someone had a similar experience before.

Employer "A" has applied for my EP, at this moment I've just got my FIN number but haven't process my EP but I requested for a clause in my contract that stipulates that if this "X" company offers me a position I can quit.

Right now company "X" might offer me a position. What I need to know is IF is ok to change employers that quick?